So, what's the truth? Is fasting really good for us, or is going without food for long periods harmful for our systems in the long run? I'm going to present both sides of the argument here, and point out a couple of possible middle-way solutions that could settle it once and for all.
The benefits of fasting
The first, unarguable benefit of fasting is logical - weight loss. However, some studies have discovered additional advantages as follows:
- Lowering blood pressure and cholesterol: these can lead to an increased risk of cardiovascular disease, (1).
- Regulating insulin sensitivity: if the body is desensitised to insulin, the result could be elevated blood sugar and an increased risk of developing diabetes, (2) (3).
- Regenerating the immune system: studies have shown that fasting can have a positive effect on the immune system (4).
Logically, fasting should therefore be healthy for us, leading to lean, vigorous bodies and longer lifespans - yet scientists still argue against the practice. Even though various experiments support the idea that short periods of fasting can yield better results in medical therapies, one shouldn't jump into it without knowing the potential consequences.
Dangers of the practice
If fasting has such great effects on the body, why do some experts advise against it, or at least, warn us to use fasting with caution?
The first important point is that they aren't attacking fasting in general, as it's a practice that's widespread and appears in every culture. Additionally, sleeping counts as a kind of fasting (ever wondered where the term break-fast comes from?), so we couldn't fully avoid it even if we tried. And sleeping is healthy, right?
The key point they are making is that fasting is not necessarily the best way to lose weight, because however many kilos you shed will be just as quick to jump back on once you go back to your normal eating patterns.
So, let's see what you need to know if you do plan on engaging in the practice of fasting.
Fasting can be dangerous if your body is not used to eating a healthy diet, you have immune problems or if you're on certain kinds of medication.
Otherwise, there are certain side effects that you could experience during a fasting period, (5):
- increased stress and sleep problems due to not consuming the amount of food you're used to
These side effects can be minimised if you make some sensible decisions, such as keeping yourself hydrated and introducing fasting to your body in small steps.
Additionally, there are some people who certainly shouldn't consider fasting (6), including:
- pregnant women
- malnourished or underweight people
- those with cardiac or hepatic disorders
- those below 18 years of age
- type one diabetics
So what's the middle way?
Having seen the reasons for not fasting, we raise the question: should you do it if it has potential consequences?
There is an approach known as ‘intermittent fasting’ which means that you reduce the amount you eat for short periods of time. The 5:2 Diet works on the principle of eating normally for 5 days per week and restricting calories to 500 calories for women and 600 calories for men on each of the remaining two days. This diet claims to help you lose weight whilst also enjoying some of the health benefits we have listed above, (7).
In addition, a team of scientists has developed a diet which replicates the effects of fasting in the body, without imposing the negative side effects on your system.
It's called the fasting-mimicking diet or FMD. This diet simulates the effects of fasting with low protein and carbohydrates. With the test run, people followed the diet for 5 days per month over a period of 3 months and found that they lost weight. They also noticed a reduction in blood pressure, body fat, and waist size, (8).
The FMD is still under investigation to discover the full scope of its effects. In the meantime, it’s important to remember to always consult a doctor or nutrition expert prior to engaging in any kind of fasting or dietary change.
(1) Salah Mesalhy, A. (2014). ‘Role of Intermittent Fasting on Improving Health and Reducing Diseases’. International Journal of Health Sciences. July 2014 (online). Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4257368/
(2) National Institute of Diabetes, Digestive and Kidney Diseases (2017). Prediabetes and Insulin Resistance. Available at:
(3) Patterson, R et al. (2015). ‘Intermittent Fasting and Human Metabolic Health’. Journal of the Academy of Nutrition and Dietetics 115(8): 1203–1212. August 2015 (online).
Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516560/
(4) Longo, V and Mattson, M (2014). ‘Fasting: Molecular Mechanisms and Clinical Applications’. Cell Metabolism 19(2): 181–192. February 2014 (online).
Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3946160/
(5) Whiteman, H (2015). Medical News Today. Fasting: health benefits and risks
Available at: https://www.medicalnewstoday.com/articles/295914.php
(6) Bailey, C and Schenker, S (2016). ‘Who Should Not Follow a Low Calorie Diet’ in The 8-Week Blood Sugar Diet. London: Short Books, p17.
(7) Mosley, M and Spencer, M (2014). ‘The Fast Diet in Practice’ in The Fast Diet: Lose Weight, Stay Healthy, Live Longer. New York: Atria Paperback, p75-150.
(8) Leslie, M (2017). ‘Five-day fasting diet could fight disease, slow aging’. Science Magazine. February 2017 (online). Available at: